Postgraduate student Dubovkina I.

The Institute of Engineering Thermophysics of National Academy of Sciences of Ukraine

How to increase the power efficiency in the technological lines of spray drying

Increase of efficiency of productions - large consumers of heat energy, can be reached by recycling of their waste energy.

Owing to intensive increase of the prices for energy carriers the great value is got by problems connected with rational use of energy and active methods of use of scientific and technical achievements which provide production improvement of quality at saving use of fuel at the expense of use of secondary resources.

Spray drying, being a component of many technologies, is among the most power-intensive technologies.

The spray drying method, thanks to extremely developed surface of contact of phases, is one of the most intensive and quickly proceeding methods of dehydration of liquid materials and products. At spray drying processes diameters of drops make tens micron that causes except a considerable surface of evaporation (1liter of the solution with the diameter of drops 40 micron has evaporation surface 150м² ) as well high intensity moisture exchange, thanks to the big difference of temperatures (150-200⁰С) between the heat-transfer agent and a material.

At the same time in comparison with other methods of drying the given method is more power expenditure, because of use of considerable volumes of the heat-transfer agent for realization of process of drying sprayed product in volume of the chamber.

In respect of economy of power resources sharply there is a question of decrease in losses of heat and reduction of power inputs in heat - and mass-transfer the devices used for spray drying of disperse materials as process spray drying is one of the most power-intensive technological processes. In view of necessity of transfer of water from liquid in a vaporous condition, and also use of great volumes of the high-temperature heat-transfer agent process realization of spray drying demands considerable power expenses.

From the analysis of power expenses spray drying chamber of industrial technological lines follows, that the greatest losses of heat are caused exhaust in a drying process heat-transfer agent and heat losses in environment (fig. 1).

Thus, there are obvious basic ways of increase of heat profitability spray drying installations:

- to reduce losses of heat with exhaust in a drying process heat-transfer agent (or rational use of this kind of waste energy);

1 - losses with exhaust in a drying process heat-transfer agent; 2 - losses with flying steam; 3 - losses with a dried up material; 4 - other expenses;

Figure 1 – Distribution of power expenses in industrial technological lines of spray drying.

- to reduce losses in environment.

Declining of power losses and increasing of power efficiency in the technological lines of the spray drying it can be attained for an account:

- utilizations of heat of waste gases from autonomous heat-generator for the previous heating of heat-transfer agent;

- utilizations of heat of exhaust in a drying process heat-transfer agent.

The realization of measures of similar type needs, as a rule, creation and designing of utilization or technological equipment.

For recuperation heat in technological processes usually use plate-type heat exchangers, rotary heat exchangers (recuperators), run-around coils, and also recuperators on heat pipes [1].

The advantages of using heat pipes over conventional methods is that large quantities of heat can be transported through a small cross-sectional area over a considerable distance with no additional power input to the system, (except for the fans to drive the airstreams) together with simplicity of design and ease of manufacture [2], [3]. The device contains rows of finned tubes partially filled with refrigerant and permanently sealed. Heating one side of a heat pipe establishes a continuous process within it whereby the warmer side acts as an evaporator and the colder side a condenser [4].

Preliminary there was investigated a possibility of the using in the capacity of a recuperator on the heat pipes of serial heat-exchange vehicles of type «freon – air», which are used in a refrigeration technique and equipment on the pilot spray drying plant of The Institute of Engineering Thermophysics of National Academy of Science of Ukraine.

Hereafter the work of industrial prototype of heat utilizer, on one of the plant of Ukraine will test during the utilization of waste gases from autonomous heat-generator, that provides work of the spray drying unit.

Bibliography:

1. O. G. Burdo, I. V. Bezbah Rotating heat pipes in devices for heat treatment of the food- stuffs // Applied Thermal Engineering 28 (2008) 341-343.

2. Leonard L. Vasiliev. Heat pipes in modern heat exchangers // Applied Thermal Engineering. – 2005. – № 25. – P. 1–19.

3. Casarosa C., Latrofa E., Shelginski A. The geyser effect in a two phase thermo-syfone // Int. Gournal of Heat and Mass Transfer. V. 26. 1983. № 6. P.933–941.

4. Shelghinski A. Tubi di calore a media temperatura. // ATTI del XXXVI Congresso Nazionale ATI dell Associazione Termotecnica Italiana. Volume Viaregio: 1981. P. 739–752.